It would appear that the BlackBerry Enterprise Server (BES) with its Mobile Data Service (MDS) is so stable that nobody dreams of implementing it in a failsafe fashion. Or so at least, according to our contact at Vodafone. I find that hard to believe. I have no reason to doubt that BES is rock solid, but what about the hardware and operating system it runs on? Is that also rock solid? What if it fails and the BES goes South? Does that mean that all mobile devices are left dangling somewhere around Earth without a line home? Oh, come on! There must be some way of getting BES clustered? If there is, the documentation hides it well: I cannot find any mention of clustering since BES version 2. A Microsoft cluster might do the trick, but I don't want to go that way if I can avoid it... What will it be? Well, Linux with VMware Server (which appears to have silently reached 1.0), HeartBeat and DRBD as a shared storage. Sounds crazy? It is. But I'm going to give it a shot. The important bit seems to be that the BES always connects to the RIM using the same IP address with SRP key, otherwise RIM supposes you've handed out your authorization key and simply cut you off. In any case that sounds quite plausible. Putting the whole BES together with its Lotus Domino in a VMware appliance and sharing that appliance over DRBD seems a viable option to me. The only thing left to do is to have HeartBeat start the VMware service on the currently active node.